Collective fluctuations in the finite-size Kuramoto model below the critical coupling: Shot-noise approach

The Kuramoto model, a paradigmatic framework for studying synchronization, exhibits a transition to collective oscillations only above a critical coupling strength in the thermodynamic limit. However, real-world systems are finite, and their dynamics can deviate significantly from mean-field predictions. Here, we investigate finite-size effects in the Kuramoto model below the critical coupling, where the theory in the thermodynamic limit predicts complete asynchrony. Using a shot-noise approach, we derive analytically the power spectrum of emergent collective fluctuations and demonstrate their dependence on the coupling strength. Numerical simulations confirm our theoretical results, though deviations arise near the critical coupling due to nonlinear effects. Our findings reveal how finite-size fluctuations sustain transient synchronization in regimes where classical mean-field theories fail, offering insights for applications in neural networks, power grids, and other coupled oscillator systems.